"We didn't see or hear any signs of life out there today," said Snohomish County Fire District 21 Chief Travis Hots on Sunday night. "It's very disappointing to all emergency responders on scene."

The mudslide is believed to have been caused by a recent heavy rainfall that caused uneven ground. It struck a former fishing village of small homes, some close to 100 years old.

Washington state Gov. Jay Inslee said on Monday that he received assurance from FEMA that the federal government will be providing assistance.

"I want to thank [FEMA Regional Administrator] Mr. [Kenneth] Murphy for this quick response to the needs of a community devastated by last week's mudslide," Inslee said in a statement. "This was a priority for the state and our Congressional delegation and means we will receive immediate assistance from specialists and clears the way for more aid in search and rescue, recovery and rebuilding."

The governor also assured families that there is a "full scale, 100 percent aggressive rescue" going on right now to find their missing loved ones.

The region has been experiencing particularly heavy rainfall this season, with Jonathan Erdman, senior meteorologist for The Weather Channel, reporting: "Through March 21, Seattle was only 0.69 inches away from tying their wettest March on record, set in 1950."

Authorities have urged everyone who might have possibly been in the area to call in and confirm their status.

"Even if you were not in the area but there might be a possibility that friends and family may believe you were in the area for whatever reason, please call this number to confirm you were OK," authorities stated.